Abstract
We analyse Rossi X-ray Timing Explorer (RXTE) and Swift observations of SWIFT J1729.9−3437 after its outburst from 2010 July 20 to 2010 August 12. We calculate a spin frequency and spin frequency derivative of 1.8734(8) × 10−3 Hz and 6.42(6) × 10−12 Hz s−1, respectively from the quadratic fit of the pulse arrival times. The quadratic fit residuals fit well to a circular orbital model with a period of 15.3(2) d and a mass function of about 1.3 M, but they can also be explained by a torque noise strength of 6.8 × 10−18 Hz s−2. Pulse profiles switch from double peaked to single peaked as the source flux continues to decrease. We find that the pulse shape generally shows no strong energy dependence. The hardness ratios reveal that the source becomes softer with decreasing flux. We construct a single spectrum from all the available RXTE and Swift observations. We find that adding an Fe line complex feature around 6.51 keV slightly improves the spectral fit. We also find that Fe line flux correlates with X-ray flux which might indicate the origin of the Fe emission as the source itself rather than the Galactic ridge.